The present disclosure relates to an image processing apparatus and an image processing method that perform various types of image processing for color image data and monochrome image data.
An image processing apparatus such as a printer or a multifunction peripheral that supports color printing prints a monochrome image or a color image on a paper sheet based on monochrome image data or color image data inputted as image data (hereinafter, referred to as “document sheet data”) of a document sheet that is a print processing target. As an image processing apparatus of this type, a configuration having a so-called tandem-type image forming portion in which photosensitive drums respectively corresponding to four colors of C (cyan), M (magenta), Y (yellow), and K (black) are provided in series, is known. It is noted that respective toner images formed on the photosensitive drums corresponding to C, M, Y, and K are transferred onto an intermediate transfer belt in an overlapping manner, and then transferred from the intermediate transfer belt onto a paper sheet.
In addition, the image processing apparatus may be provided with a main control portion that performs overall control for the entire apparatus, and an engine control portion that controls the operation of an image forming portion. The main control portion includes an image processing portion that performs various types of image processing such as rotation processing, halftone processing, or size cut processing for image data. It is noted that the main control portion uses a storage memory such as an SDRAM, as a working area.
On the other hand, the engine control portion executes a color print operation using the respective photosensitive drums for C, M, Y, and K in the case where document sheet data is color image data, and executes a monochrome print operation using only the photosensitive drum for K in the case where document sheet data is monochrome image data. Specifically, upon the monochrome print operation, the engine control portion separates the photosensitive drums for C, M, and Y from the intermediate transfer belt.
In addition, in the case where document sheet data is mixed document sheet data including both monochrome image data and color image data, the engine control portion selectively executes one of the monochrome print operation and the color print operation so as to reduce a print time as much as possible. That is, even if document sheet data is monochrome image data, the engine control portion may execute the color print operation. Therefore, in the case where document sheet data is monochrome image data, the main control portion generates color image data by adding dummy image data pieces for C, M, and Y to the monochrome image data. Thus, image data inputted to the engine control portion is always color image data, and therefore the engine control portion can optionally execute one of monochrome print operation and color print operation.
Here, FIGS. 7A and 7B are diagrams for explaining a print operation in the case where document sheet data is monochrome image data. FIG. 7A shows an output timing of color image data in the case where the color print operation is executed, and FIG. 7B shows an output timing of color image data in the case where the monochrome print operation is executed. The color image data is generated by the main control portion and stored into the SDRAM of the main control portion.
First, as shown in FIG. 7A, upon the color print operation, the engine control portion sequentially reads image data pieces for respective colors of C, M, Y, and K from the SDRAM of the main control portion at predetermined timings in accordance with the placement intervals among the respective photosensitive drums. In this case, the same print time as in the case where document sheet data is color image data is required.
On the other hand, as shown in FIG. 7B, upon the monochrome print operation, the engine control portion simultaneously reads image data pieces for respective colors of C, M, Y, and K from the SDRAM of the main control portion. In this case, since the image data pieces for respective colors of C, M, Y, and K are simultaneously outputted, the print operation is executed in a shorter time than in the case of the color print operation.